Donald Trump has pledged post-election lawsuits against every woman who has accused him of sexual assault or other inappropriate behaviour.

Mr Trump made the claim as he accused Hillary Clinton's campaign and the Democratic Party of orchestrating the allegations.

"Every one of these liars will be sued once the election is over. I look so forward to doing that," Mr Trump said.

The threat overshadowed his intended focus during a speech in Gettysburg, Pennsylvania, that was billed as a chance for the Republican nominee to lay out his agenda for his first 100 days in office.

Mr Trump promised to institute a hiring freeze on federal workers and to label China as a currency manipulator, but he first seized on the chance to once again try to discredit his accusers.

"Every woman lied when they came forward to hurt my campaign," he said.

Ten women have publicly accused Mr Trump of unwanted advances or sexual assault in the weeks since a 2005 recording emerged in which the former reality TV star made sexually aggressive comments about women.

Mr Trump has denied all allegations while insisting some of the women were not attractive enough for him to want to pursue.

He also stuck to his belief the election is "rigged against him," repeated concerns about widespread voter fraud and insisted Ms Clinton should have been barred from running because of legal questions about her use of a private email system as secretary of state.

Mr Trump complained that a "corrupt" media is fabricating stories in order to make him "look as bad and dangerous as possible".

Ms Clinton, meanwhile, has been displaying growing confidence and making direct appeals to voters "who may be reconsidering their support" for Mr Trump following a string of sexual assault allegations and other troubles for the GOP nominee.

"I know you may still have questions for me," she said on Friday in Cleveland, Ohio. "I respect that. I want to answer them. I want to earn your vote."

Her campaign headquarters in New York was back up and running after an envelope containing a white powdery substance arrived on Friday, triggering an evacuation of the 11th floor.

Police said initial tests showed the substance was not harmful and Clinton spokesman Glen Caplin said four people who received a full medical examination reported no health issues and were released.

Ms Clinton was also getting a campaign boost on Saturday from singer Katy Perry, who planned to push early voting during an event in Las Vegas.

The pop icon has been a vocal Clinton backer and was the featured entertainment at the Democratic National Convention.